Moving machinery wears, changing the dimensions of its components. Sufficient wear will seriously degrade the performance of the machinery, thus wear of moving parts must be accommodated or repaired so that the efficiency, reliability and useful life of the machinery are all increased. For example, it is well known that turbine valve seats and other related surfaces wear. These surfaces are restored to their original dimensions either by welding, machining or a combination of these two processes. In order to machine a valve body, it is presently necessary to use three separate machine tools, requiring three different set-up procedures. In addition, current practice for machining a valve body requires that the machinist reach inside the valve body to mount and clamp the cutting tool to the tool bar.
Apparatus that are attached to a steam turbine to machine valve seats are known. U.S. Pat. No. 4,678,379--Sunday discloses an apparatus for machining a stop valve seat ring by mounting a shaft on two fixtures and providing a tool support mounted on the shaft. A motor rotates the shaft and tool support, thereby moving a tool to machine the seat ring. U.S. Pat. No. 5,030,041--Marron discloses a compact boring system for machining the interior surface of steam turbine valves and rotors in the field. The disclosed device also provides a rotatable shaft that mounts within the cylindrical object being machined. The drive system and cutting head are formed as a single unit and can travel axially along the central, rotatable shaft. Both of the aforementioned references are assigned to the assignee of the present invention and are fully incorporated herein by reference.
It would thus be desirable to streamline valve seat machining procedures. The re-machining and restoration of turbine valve seats is the type of operation that is repeated a number of times, thus any savings of time and materials will be multiplied to a great benefit. Therefore, it is an object of the present invention to provide methods and apparatus that reduce the complexity of valve seat machining procedures as well as similar procedures.